Symmetry-induced Growth of Two-dimensional Ferromagnetic γ-Fe₂O₃

Abstract

Two-dimensional (2D) iron oxide has aroused particular interest for its important roles in exploring fundamental physics and emerging spintronics. As a unique 2D ferromagnetic material with a nonlayered structure, γ-Fe₂O₃ exhibits many intriguing magnetic properties. However, since γ-Fe₂O₃ is metastable and tends to transform into α-Fe₂O₃, producing high-quality pure γ-Fe₂O₃ remains a challenge. Herein, we have successfully synthesized 2D γ-Fe₂O₃ nanotriangles with pure phase and high Curie temperature via a substrate symmetry-induced strategy. Since the atoms in the top layer of the sapphire substrate generally have six-fold symmetry, γ-Fe₂O₃ nanotriangles exhibit two orientations, including 0° and 60° antialigned domains. Furthermore, we observe a pronounced incidence of merged growth both among 0°–0° and 0°–60° nanotriangles. Magnetic force microscopy (MFM) reveals that the individual nanotriangle γ-Fe₂O₃ exhibits the typical ferromagnetic vortex state, whereas the domain is prominently suppressed in merged nanotriangles. This work provides novel insights into 2D ferromagnetic materials, marking a pivotal step toward their practical deployment in high-performance spintronic and quantum devices.

Keywords

Nonlayered 2D γ-Fe₂O₃ / Symmetry-induced / Merged growth / Ferromagnetism

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Jilin University, The Editorial Department of Chemical Research in Chinese Universities and Springer-Verlag GmbH